Casus belli

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A Casus Belli, sometimes abbreviated CB and meaning "Cause for War" in Latin, represents a justification for war that is recognized as legitimate by other characters. A ruler must have a valid Casus Belli in order to be able to declare war upon another ruler and can only gain from a war what the Casus Belli specifies.

War Target[edit]

The War Target is the map region which is targeted by a Casus Belli. If the Casus Belli does not target a map region then the defender's Realm Capital becomes the War Target.

The attacking side gains more War Score by occupying Holdings locates in the War Target region. After a grace period the defender will passively gain War Score by holding all Counties in the War Target region.

CB list[edit]

Each Casus Belli will cost  Prestige and/or  Piety. If a character cannot pay the cost it can pay with a Level of Prestige or Level of Devotion instead. Declaring war against a character's Head of Faith costs 500 Piety if the Head of Faith is Spiritual and 100 Piety if Head of Faith is Temporal.

Casus Belli costs can be removed via one of the game rules.

Casus Belli Requirements Cost War outcome victory.png Enforce Demands effect War outcome white peace.png White Peace effect War outcome defeat.png Surrender effect
Independence War Target is the Liege 500 Prestige if not Tribal
250 Prestige if Tribal
Attacker becomes independent Attacker stays a vassal Attacker stays a vassal
Defender imprisons the attacker
Defender gains title revocation reason
Claims Claim on the target
 Rightful Ownership innovation if another character's Claim
 Divine Right innovation if own Claim
100 Prestige per County (own claim)
200 Prestige per Duchy (own claim)
400 Prestige per Kingdom (own claim)
800 Prestige per Empire (own claim)
250 Prestige per County (other's claim)
500 Prestige per Duchy (other's claim)
1000 Prestige per Kingdom (other's claim)
3000 Prestige per Empire (other's claim)
Claimant gains the targeted Titles
Attacker gets a Weak Hook on Claimant
Defender keeps their titles Defender keeps their titles
Claimant loses the Claims used
Subjugate Yes One of the following
  • Tribal government, Distinguished level of fame, and the Target has Tribal Government
  • Eastern religion and Exalted among Men level of fame, and the Target follows an Eastern Religion
  • Temporal Head of Faith and Devoted Servant level of devotion, and the Target shares your Faith
1000 Prestige if not Tribal
500 Prestige if Tribal
Attacker becomes the defender's liege Defender stays independent Defender stays independent
Attacker's Factions gain Discontent
Raid for Captives Core tenet flagellant.png Faith has the Human Sacrifice tenet 80 if faith has the Armed Pilgrimages tenet
100 if faith hasn't the Armed Pilgrimages tenet
Attacker imprisons 3-5 of the defender's courtiers Attacker gains no prisoners Defender gets 3-5 prisoners if same tenet
Excommunication War Yes Same faith
Yes Target is independent
Target has the Excommunicated trait
None Defender suffers succession Defender keeps their titles Defender keeps their titles
Defender loses the Excommunicated trait
Attacker loses Opinion with Head of Faith
Ducal Conquest of County Diplomacy lifestyle.png Conquest lifestyle perk
De jure cb.png Attacker owns a County in the same uncreated Duchy
350 Prestige if target's title rank is Count
750 Prestige if target's title rank is above
Attacker gains the targeted County Defender keeps their titles Defender keeps their titles
Attacker's Factions gain Discontent
Forced Vassalization Diplomacy lifestyle.png Forced Vassalage lifestyle perk
Yes Target is an independent neighbouring realm
No Target is not a Holy Order or Head of Faith
125 Prestige per County Attacker becomes the defender's liege Defender stays independent Defender stays independent
Attacker's Factions gain Discontent
Laudably Conquer County Request Claim on Ireland decision
Yes Target is in the Hibernia region
No Do not have the same Liege
150 Prestige if Feudal and different faith
75 Prestige if Tribal and different faith
100 Piety if Feudal and same faith
50 Piety if Tribal and same faith
Attacker gains the defender's titles Defender keeps their titles Defender keeps their titles
Attacker's Factions gain Discontent
Mongol Invasion of Kingdom Mongol Empire title
Established level of fame
Yes Tribal government
Yes Realms are adjacent
200 Prestige Attacker takes all titles from Hostile/Evil faiths
Attacker vassalizes all rulers of other faiths
Defender keeps their titles Defender keeps their titles
Attacker's Factions gain Discontent
Restore Imperial Province Roman Empire title
De jure cb.png Duchy was part of the Roman Empire
Yes Religion is Christian or Greco-Roman
None Attacker gains the targeted Duchy Defender keeps their titles Defender keeps their titles
Attacker must pay war reparations

De Jure CBs[edit]

All Title owners have a De Jure CB towards characters who own a lower Title that belongs to the de jure territory of the higher Title. All De Jure CBs cost 100  Prestige per County in the War Target Title and have a War Contribution Share of 300  Prestige.

  • If the war ends by enforcing demands the attacker will gain the War Target Title and if it's a Vassal its Liege will gain a  Weak Hook on them
  • If the war ends by white peace the defender keeps the War Target Title
  • If the war ends by surrender the defender's keeps the War Target Title and the attacker must pay  Gold
War Target rank Required Innovation
 County Casus Belli
 Duchy  Chronicle Writing
De jure cb.png All Titles  Rightful Ownership

Conquest CBs[edit]

The following CBs are only available to Rulers who have Clan or Tribal government or whose Faith has the Warmonger or Pursuit of Power tenets.

  • If the war ends by enforcing demands the attacker will gain the War Target Title and Fame equal to the War Contribution Share
  • If the war ends by white peace the defender keeps the War Target Title and the attacker loses 75  Prestige
  • If the war ends by surrender the defender's keeps the War Target Title and the attacker must pay  Gold and gain +25 Faction Discontent
War Target rank Required Level of Fame Same Faith cost Different Faith cost War Contribution Share Once per lifetime
 County Established
  • 50 if character has Tribal government
  • 100 if character has Clan government
  • 75 if character has Tribal government
  • 150 if character has Clan government
75 No
 Duchy Icon prestige 03.png Illustrious
  • 250 if character has Tribal government
  • 500 if character has Clan government
  • 375 if character has Tribal government
  • 750 if character has Clan government
150 No
 Kingdom Icon prestige 04.png Exalted Among Men 2000 2000 350 Yes

Holy War CBs[edit]

The following CBs will cause a Holy War instead of a regular one and require the Faith to be organized and to not have the Pacifism or Dharmic Pacifism tenets and can only target rulers whose Faith is considered Hostile or Evil.

  • If the war ends by enforcing demands the attacker will gain all Titles held by Rulers of different Faith and vassalize all Rulers of the same Faith in the War Target region. The attacker's faith loses the  Fervor cost and the defender's faith gains the twice that amount.
  • If the war ends by white peace the defender keeps all their Titles and the attacker loses 50  Piety
  • If the war ends by surrender the defender's keeps all their Titles, the attacker must pay  Gold and gain +25 Faction Discontent and -15 Vassal Opinion for 5 years
War Target rank Required Level of Devotion  Fervor cost  Piety cost (without Armed Pilgrimages tenet)  Piety cost (with Armed Pilgrimages tenet) War Contribution Share Once per lifetime
 County Dutiful 1 100 80 100 No
 Duchy Faithful 2 200 160 200 No
 Kingdom Paragon of Virtue 5 750 600 500 Yes

Migrate to Pannonia[edit]

Migrate to Pannonia is a unique Casus Belli with special mechanics that can only be used once per game by characters of Táltosist faith who make the Prepare to Cross the Carpathians decision against characters in the Pannonian Basin region. If the Hungarian Migration game rule is set to Immediate the game will start with the casus belli being used by Grand Prince Álmos Ügyekfi of the Mogyër Confederation against King Boris of Bulgaria.

If the war ends in white peace the defender keeps his or her titles and if it ends in surrender the attacker's factions will also gain discontent. If the war ends by enforcing demands however it will have the following effects:

  • Attacker gains all titles held by the defender in the Pannonian Basin region
  • Attacker gains the Kingdom of Hungary title, which replaces Kingdom of Pannonia
  • Any other kingdom title held by the attacker is destroyed
  • Any held title that is not within the de jure realm of Kingdom of Hungary is given to another character
  • All vassals that are not within the de jure realm of Kingdom of Hungary become independent
  • All controlled counties convert to Mogyër culture and Táltosist faith
  • All previously controlled counties convert to Pecheneg culture

When the Casus Belli is used it will spawn the following army for as long as the attacking character lives:

Years  Levies Unit horse archers.png Horse Archers
867-889 3000 2000
890-904 5000 3000
905+ 6000 4000

Varangian Adventure[edit]

Varangian Adventure is a unique Casus Belli with special mechanics that can only be used during the Tribal Era on Counties and Duchies owned by characters from a different Culture Group and costs 1000  Prestige. To be used it requires the Varangian Adventurers innovation, which is only available to North Germanic cultures and requires the Northern Lords DLC. The Casus Belli can be used multiple times but each use will cost 1000 more  Prestige than the previous one. It cannot be used by Kings or Emperors.

If the war ends in white peace the defender keeps his or her titles and if it ends in surrender it must also pay  Gold and  Prestige to the attacker. If the war ends by enforcing demands however it will have the following effects:

  • All titles held by the attacker are destroyed or given to other characters
  • All vassals are given independence
  • Attacker gains the War Target title and all titles that are de jure part of it
  • Attacker gains the  Adventurer trait
  • Attacker gains 200  Gold
  • If the War Target title was a County and its de jure Duchy does not exist or is part of the defender's realm the Duchy is given to the attacker

When the Casus Belli is used for the first time it will spawn the following for the duration of the war the following army based on the number of owned Counties of the same Faith and Culture in the region of Mainland Scandinavia:

Counties  Levies Unit varangian veterans.png Varangian Veterans Unit bondi.png Bondi Unit vigmen.png Vigmen Unit danish huskarls.png Huscarls
1 100 100 0 0 0
2 100 300 0 0 0
3 100 300 200 0 0
4 100 300 400 0 0
5 100 300 400 200 0
6 100 300 400 400 0
7 100 300 400 600 0
8 100 300 400 800 0
9 100 300 400 800 200
10 100 300 400 800 400

In addition if the character's Dynasty unlocked the first Adventure legacy track.png Adventure Dynasty Legacy it will gain an additional 100  Levies, 400 Unit varangian veterans.png Varangian Veterans, 100 Unit bondi.png Bondi and 400 Unit vigmen.png Vigmen.

AI Rulers will only use the Casus Belli if all their held titles are located in the Mainland Scandinavia region. If the Scandinavian Adventurers game rule is not set to Apocalyptic then they also require the  Ambitious trait, as well as at least two of the following traits:  Adventurer,  Arrogant,  Brave,  Greedy.

Characters CharactersAttributesTraitsResourcesLifestyleDynastyCultureInnovationsModifiers
Realm & Governance VassalsCouncilCourtSchemesGovernmentLawsDecisionsTitlesBaronyCounty
Warfare WarfareCasus belliAllianceArmyHired forces
Faith ReligionFaithDoctrinesTenets
Meta ModdingPatchesDownloadable contentDeveloper diariesAchievementsJargon